Chitosan is a non-toxic cationic copolymer of N-acetyl-D-glucosamine and D-glucosamine. Chitosan can form a complex with nucleic acid and has been used as a DNA delivery vehicle to transfect cells.
There is difficulty in producing a concentrated solution of chitosan-nucleic acid complexes. Increasing the concentrations of chitosan and nucleic acid in a mixing solution leads to precipitation as well as undesirable variation in the size of chitosan-nucleic acid complexes so produced. Additionally, increasing the concentration of chitosan-nucleic acid complexes in a prepared solution leads to the aggregation of complexes and precipitation from solution.
The use of concurrent flow mixing to produce uniform particles comprising DNA and condensing agents (e.g., polycationic carbohydrates) has been described (U.S. Pat. No. 6,537,813). To produce such particles, DNA solution and condensing agent solution may be concurrently and separately introduced into a flow through mixer that comprises a static or dynamic mixer which provides for mixing and particle formation. Maintaining the proper ratio of DNA and condensing agent throughout the introduction and mixing processes is reportedly important and a significant deviation from charge neutrality can lead to either incomplete condensation or particle aggregation in the process.